[PATCH v13 11/11] KVM: x86: Enable CET virtualization and advertise CET to userspace

Yang Weijiang
2020-07-01T08:05:17Z

Set the feature bits so that CET capabilities can be seen in guest via
CPUID enumeration. Add CR4.CET bit support in order to allow guest set CET
master control bit(CR4.CET).

Disable KVM CET feature once unrestricted_guest is turned off because
KVM cannot emulate guest CET behavior well in this case.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/include/asm/kvm_host.h | 3 ++-
arch/x86/kvm/cpuid.c | 5 +++--
arch/x86/kvm/vmx/vmx.c | 5 +++++
arch/x86/kvm/x86.c | 5 +++++
4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f68c825e94ad..21f3c89d8c70 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -95,7 +95,8 @@
| X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \
| X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \
| X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_VMXE \
- | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP))
+ | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP \
+ | X86_CR4_CET))

#define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 984ab2b395b3..333a9e0d7cdf 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -344,7 +344,8 @@ void kvm_set_cpu_caps(void)
F(AVX512VBMI) | F(LA57) | 0 /*PKU*/ | 0 /*OSPKE*/ | F(RDPID) |
F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
- F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/
+ F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/ |
+ F(SHSTK)
);
/* Set LA57 based on hardware capability. */
if (cpuid_ecx(7) & F(LA57))
@@ -353,7 +354,7 @@ void kvm_set_cpu_caps(void)
kvm_cpu_cap_mask(CPUID_7_EDX,
F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
- F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM)
+ F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) | F(IBT)
);

/* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 70cb2d4a1391..7dac5747adc8 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7411,6 +7411,11 @@ static __init void vmx_set_cpu_caps(void)
/* CPUID 0x80000001 */
if (!cpu_has_vmx_rdtscp())
kvm_cpu_cap_clear(X86_FEATURE_RDTSCP);
+
+ if (!enable_unrestricted_guest) {
+ kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
+ kvm_cpu_cap_clear(X86_FEATURE_IBT);
+ }
}

static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 94ca5b56d233..a4cf5f3211f3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9707,6 +9707,11 @@ int kvm_arch_hardware_setup(void *opaque)
if (kvm_cpu_cap_has(X86_FEATURE_XSAVES))
supported_xss = host_xss & KVM_SUPPORTED_XSS;

+ if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK) &&
+ !kvm_cpu_cap_has(X86_FEATURE_IBT))
+ supported_xss &= ~(XFEATURE_MASK_CET_USER |
+ XFEATURE_MASK_CET_KERNEL);
+
cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data);

if (kvm_has_tsc_control) {
--
2.17.2